Touch assembly and method are described for fabricating a spliced low-loss, high-strength optical transmission line. A first fiber is spliced to a second fiber at a splice point. The spliced fibers are loaded into a heat treatment station, where a gas torch flame is used to thermally treat a splice region including the splice point, with the thermal treatment reducing splice loss due to expansion and mismatch of modefields between the first and second fibers. While heating the splice region, a dry gas is purged around the torch flame during the heat treatment process to avoid water at the surface of the spliced fibers. A purging gas is fed to the torch flame to purge dust particles from the flame, and after the heat treatment has been completed, the torch flame is used to restore the glass surface of the spliced fibers. Additionally described are torch assemblies for fabricating low-loss, high-strength optical fiber transmission lines.